The single proton hydrogen isotope exchange rates of proteins will be studied. The exchange of peptide NH protons in aqueous solutions is a measure of the accessibility of solvent species to the polypeptide backbone in the folded, closely packed, solution structure. Hydrogen exchange kinetics is the only method available for the measurement of long time motions in folded proteins in solution. The study of a single proton exchange rates is a significant advance in this area as the kinetic analysis is far more tractable than that of techniques in which all labile protons exchange simultaneously. The single proton exchange data also allows assignment of the proton to a specific residue in the protein three-dimensional structure. The hydrogen-deuterium exchange rates will be measured by NMR. In addition to the direct measure of the proton resonance in deuterium solvent, a number of other techniques will be tested for general applicability to the elucidation of single proton exchange kinetics. These include partial labeling procedures and NMR spectroscopic techniques. In addition to the small globular proteins, BPTI and cytochrome c, we will continue the structural characterization of E. coli L7 and L12 ribosomal proteins and neurospora crassa L7/L12-like ribosomal proteins. In my laboratory these proteins have been shown to possess a number of unusual properties. We will continue to determine the structural basis of these properties, and move to the NMR and H-D studies of the E. coli and neurospora proteins and their fragments.